/Engine/Source/Runtime/ImageCore/Public/DDSFile.h
For 8-bit UNorm formats, both RGBA and BGRA channel order variants exist and are popular. This function does the trivial conversion between the two, updating both the DXGI Format and the pixel data to do so. When the channel order is already correct or the pixel format is not one of the few formats that exist in both RGBA and BGRA variants, this function does nothing.
void ConvertChannelOrder ( [EChannelOrder](API\Runtime\ImageCore\UE__DDS__EChannelOrder) InTargetOrder )